Methods of fabricating a polycrystalline diamond compact

ABSTRACT

In an embodiment, a method of fabricating a polycrystalline diamond compact is disclosed. The method includes sintering a plurality of diamond particles in the presence of a metal-solvent catalyst to form a polycrystalline diamond body; leaching the polycrystalline diamond body to at least partially remove the metal-solvent catalyst therefrom, thereby forming an at least partially leached polycrystalline diamond body; and subjecting an assembly of the at least partially leached polycrystalline diamond body and a cemented carbide substrate to a high-pressure/high-temperature process at a pressure to infiltrate the at least partially leached polycrystalline diamond body with an infiltrant. The pressure of the high-pressure/high-temperature process is less than that employed in the act of sintering of the plurality of diamond particles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/623,764 filed on 20 Sep. 2012, which is a continuation of U.S. patentapplication Ser. No. 12/690,998 filed on 21 Jan. 2010 (now U.S. Pat. No.8,297,382 issued on 30 Oct. 2012), which is a continuation-in-part ofU.S. patent application Ser. No. 12/244,960 filed on 3 Oct. 2008 (nowU.S. Pat. No. 7,866,418 issued on 11 Jan. 2011), the disclosure of eachof which is incorporated herein, in its entirety, by this reference.

BACKGROUND

Wear-resistant, superabrasive compacts are utilized in a variety ofmechanical applications. For example, polycrystalline diamond compacts(“PDCs”) are used in drilling tools (e.g., cutting elements, gagetrimmers, etc.), machining equipment, bearing apparatuses, wire-drawingmachinery, and in other mechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller cone drill bits and fixed-cutter drillbits. A PDC cutting element typically includes a superabrasive diamondlayer commonly referred to as a diamond table. The diamond table may beformed and bonded to a substrate using a high-pressure, high-temperature(“HPHT”) process. The PDC cutting element may also be brazed directlyinto a preformed pocket, socket, or other receptacle formed in a bitbody of a rotary drill bit. The substrate may often be brazed orotherwise joined to an attachment member, such as a cylindrical backing.A rotary drill bit typically includes a number of PDC cutting elementsaffixed to the bit body. A stud carrying the PDC may also be used as aPDC cutting element when mounted to a bit body of a rotary drill bit bypress-fitting, brazing, or otherwise securing the stud into a receptacleformed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented carbidesubstrate into a container with a volume of diamond particles positionedadjacent to the cemented carbide substrate. A number of such cartridgesmay be loaded into an HPHT press. The substrates and volume of diamondparticles are then processed under HPHT conditions in the presence of acatalyst material that causes the diamond particles to bond to oneanother to form a matrix of bonded diamond grains defining apolycrystalline diamond (“PCD”) table that is bonded to the substrate.The catalyst material is often a metal-solvent catalyst (e.g., cobalt,nickel, iron, or alloys thereof) that is used for promoting intergrowthof the diamond particles. For example, a constituent of the cementedcarbide substrate, such as cobalt from a cobalt-cemented tungstencarbide substrate, liquefies and sweeps from a region adjacent to thevolume of diamond particles into interstitial regions between thediamond particles during the HPHT process. The cobalt acts as a catalystto promote intergrowth between the diamond particles, which results information of bonded diamond grains.

Because of different coefficients of thermal expansion and modulus ofelasticity between the PCD table and the cemented carbide substrate,residual stresses of varying magnitudes may develop within differentregions of the PCD table and the cemented carbide substrate. Suchresidual stresses may remain in the PCD table and cemented carbidesubstrate following cooling and release of pressure from the HPHTprocess. These complex stresses may be concentrated near the PCDtable/substrate interface. Residual stresses at the interface betweenthe PCD table and cemented carbide substrate may result in prematurefailure of the PDC upon cooling or during subsequent use under thermalstresses and applied forces.

In order to help reduce de-bonding of the PCD table from the cementedcarbide substrate, some PDC designers have made the interfacial surfaceof the cemented carbide substrate that bonds to the PCD tablesignificantly nonplanar. For example, various nonplanar substrateinterfacial surface configurations have been proposed and/or used, suchas a plurality of spaced protrusions, a honeycomb-type protrusionpattern, and a variety of other configurations.

SUMMARY

Embodiments of the invention relate to PCD exhibiting enhanceddiamond-to-diamond bonding. In an embodiment, PCD includes a pluralityof diamond grains defining a plurality of interstitial regions. Ametal-solvent catalyst occupies at least a portion of the plurality ofinterstitial regions. The plurality of diamond grains and themetal-solvent catalyst collectively may exhibit a coercivity of about115 Oersteds (“Oe”) or more and a specific magnetic saturation of about15 Gauss·cm³/grams (“G·cm³/g”) or less.

In an embodiment, PCD includes a plurality of diamond grains defining aplurality of interstitial regions. A metal-solvent catalyst occupies theplurality of interstitial regions. The plurality of diamond grains andthe metal-solvent catalyst collectively may exhibit a specific magneticsaturation of about 15 G·cm³/g or less. The plurality of diamond grainsand the metal-solvent catalyst define a volume of at least about 0.050cm³.

In an embodiment, a method of fabricating PCD includes enclosing aplurality of diamond particles that exhibit an average particle size ofabout 30 μm or less, and a metal-solvent catalyst in a pressuretransmitting medium to form a cell assembly. The method further includessubjecting the cell assembly to a temperature of at least about 1000° C.and a pressure in the pressure transmitting medium of at least about 7.5GPa to form the PCD.

In an embodiment, a PDC includes a PCD table bonded to a substrate. Atleast a portion of the PCD table may comprise any of the PCD embodimentsdisclosed herein. In an embodiment, the substrate includes aninterfacial surface that is bonded to the polycrystalline diamond tableand exhibits a substantially planar topography. According to anembodiment, the interfacial surface may include a plurality ofprotrusions, and a ratio of a surface area of the interfacial surface inthe absence of the plurality of provisions to a surface area of theinterfacial surface with the plurality of protrusions is greater thanabout 0.600.

In an embodiment, a method of fabricating a PDC includes enclosing acombination in a pressure transmitting medium to form a cell assembly.The combination includes a plurality of diamond particles that exhibitan average particle size of about 30 μm or less positioned at leastproximate to a substrate having an interfacial surface that issubstantially planar. The method further includes subjecting the cellassembly to a temperature of at least about 1000° C. and a pressure inthe pressure transmitting medium of at least about 7.5 GPa to form a PCDtable adjacent to the substrate.

Further embodiments relate to applications utilizing the disclosed PCDand PDCs in various articles and apparatuses, such as rotary drill bits,bearing apparatuses, wire-drawing dies, machining equipment, and otherarticles and apparatuses.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical elements or features indifferent views or embodiments shown in the drawings.

FIG. 1A is a schematic diagram of an example of a magnetic saturationapparatus configured to magnetize a PCD sample approximately tosaturation.

FIG. 1B is a schematic diagram of an example of a magnetic saturationmeasurement apparatus configured to measure a saturation magnetizationof a PCD sample.

FIG. 2 is a schematic diagram of an example of a coercivity measurementapparatus configured to determine coercivity of a PCD sample.

FIG. 3A is a cross-sectional view of an embodiment of a PDC including aPCD table formed from any of the PCD embodiments disclosed herein.

FIG. 3B is a schematic illustration of a method of fabricating the PDCshown in FIG. 3A according to an embodiment.

FIG. 3C is a graph of residual principal stress versus substratethickness that was measured in a PCD table of a PDC fabricated at apressure above about 7.5 GPa and a PCD table of a conventionally formedPDC.

FIG. 4A is an exploded isometric view of a PDC comprising a substrateincluding an interfacial surface exhibiting a selected substantiallyplanar topography according to an embodiment.

FIG. 4B is an assembled cross-sectional view of the PDC shown in FIG. 4Ataken along line 4B-4B.

FIG. 5A is cross-sectional view of a PDC comprising a substrateincluding an interfacial surface exhibiting a selected substantiallyplanar topography according to yet another embodiment.

FIG. 5B is an isometric view of the substrate shown in FIG. 5A.

FIG. 6A is an isometric view of an embodiment of a rotary drill bit thatmay employ one or more of the disclosed PDC embodiments.

FIG. 6B is a top elevation view of the rotary drill bit shown in FIG.6A.

FIG. 7 is an isometric cutaway view of an embodiment of a thrust-bearingapparatus that may utilize one or more of the disclosed PDC embodiments.

FIG. 8 is an isometric cutaway view of an embodiment of a radial bearingapparatus that may utilize one or more of the disclosed PDC embodiments.

FIG. 9 is a schematic isometric cutaway view of an embodiment of asubterranean drilling system including the thrust-bearing apparatusshown in FIG. 7.

FIG. 10 is a side cross-sectional view of an embodiment of awire-drawing die that employs a PDC fabricated in accordance with theprinciples described herein.

DETAILED DESCRIPTION

Embodiments of the invention relate to PCD that exhibits enhanceddiamond-to-diamond bonding. It is currently believed by the inventorsthat as the sintering pressure employed during the HPHT process used tofabricate such PCD is moved further into the diamond-stable region awayfrom the graphite-diamond equilibrium line, the rate of nucleation andgrowth of diamond increases. Such increased nucleation and growth ofdiamond between diamond particles (for a given diamond particleformulation) may result in PCD being formed exhibiting one or more of arelatively lower metal-solvent catalyst content, a higher coercivity, alower specific magnetic saturation, or a lower specific permeability(i.e., the ratio of specific magnetic saturation to coercivity) than PCDformed at a lower sintering pressure. Embodiments also relate to PDCshaving a PCD table comprising such PCD, methods of fabricating such PCDand PDCs, and applications for such PCD and PDCs in rotary drill bits,bearing apparatuses, wire-drawing dies, machining equipment, and otherarticles and apparatuses.

PCD Embodiments

According to various embodiments, PCD sintered at a pressure of at leastabout 7.5 GPa may exhibit a coercivity of 115 Oe or more, a high-degreeof diamond-to-diamond bonding, a specific magnetic saturation of about15 G·cm³/g or less, and a metal-solvent catalyst content of about 7.5weight % (“wt %”) or less. The PCD includes a plurality of diamondgrains directly bonded together via diamond-to-diamond bonding (e.g.,sp³ bonding) to define a plurality of interstitial regions. At least aportion of the interstitial regions or, in some embodiments,substantially all of the interstitial regions may be occupied by ametal-solvent catalyst, such as iron, nickel, cobalt, or alloys of anyof the foregoing metals. For example, the metal-solvent catalyst may bea cobalt-based material including at least 50 wt % cobalt, such as acobalt alloy.

The diamond grains may exhibit an average grain size of about 50 μm orless, such as about 30 μm or less or about 20 μm or less. For example,the average grain size of the diamond grains may be about 10 μm to about18 μm and, in some embodiments, about 15 μm to about 18 μm. In someembodiments, the average grain size of the diamond grains may be about10 μm or less, such as about 2 μm to about 5 μm or submicron. Thediamond grain size distribution of the diamond grains may exhibit asingle mode, or may be a bimodal or greater grain size distribution.

The metal-solvent catalyst that occupies the interstitial regions may bepresent in the PCD in an amount of about 7.5 wt % or less. In someembodiments, the metal-solvent catalyst may be present in the PCD in anamount of about 3 wt % to about 7.5 wt %, such as about 3 wt % to about6 wt %. In other embodiments, the metal-solvent catalyst content may bepresent in the PCD in an amount less than about 3 wt %, such as about 1wt % to about 3 wt % or a residual amount to about 1 wt %. Bymaintaining the metal-solvent catalyst content below about 7.5 wt %, thePCD may exhibit a desirable level of thermal stability suitable forsubterranean drilling applications.

Many physical characteristics of the PCD may be determined by measuringcertain magnetic properties of the PCD because the metal-solventcatalyst may be ferromagnetic. The amount of the metal-solvent catalystpresent in the PCD may be correlated with the measured specific magneticsaturation of the PCD. A relatively larger specific magnetic saturationindicates relatively more metal-solvent catalyst in the PCD.

The mean free path between neighboring diamond grains of the PCD may becorrelated with the measured coercivity of the PCD. A relatively largecoercivity indicates a relatively smaller mean free path. The mean freepath is representative of the average distance between neighboringdiamond grains of the PCD, and thus may be indicative of the extent ofdiamond-to-diamond bonding in the PCD. A relatively smaller mean freepath, in well-sintered PCD, may indicate relatively morediamond-to-diamond bonding.

As merely one example, ASTM B886-03 (2008) provides a suitable standardfor measuring the specific magnetic saturation and ASTM B887-03 (2008)e1 provides a suitable standard for measuring the coercivity of the PCD.Although both ASTM B886-03 (2008) and ASTM B887-03 (2008) e1 aredirected to standards for measuring magnetic properties of cementedcarbide materials, either standard may be used to determine the magneticproperties of PCD. A KOERZIMAT CS 1.096 instrument (commerciallyavailable from Foerster Instruments of Pittsburgh, Pa.) is one suitableinstrument that may be used to measure the specific magnetic saturationand the coercivity of the PCD.

Generally, as the sintering pressure that is used to form the PCDincreases, the coercivity may increase and the magnetic saturation maydecrease. The PCD defined collectively by the bonded diamond grains andthe metal-solvent catalyst may exhibit a coercivity of about 115 Oe ormore and a metal-solvent catalyst content of less than about 7.5 wt % asindicated by a specific magnetic saturation of about 15 G·cm³/g or less.In a more detailed embodiment, the coercivity of the PCD may be about115 Oe to about 250 Oe and the specific magnetic saturation of the PCDmay be greater than 0 G·cm³/g to about 15 G·cm³/g. In an even moredetailed embodiment, the coercivity of the PCD may be about 115 Oe toabout 175 Oe and the specific magnetic saturation of the PCD may beabout 5 G·cm³/g to about 15 G·cm³/g. In yet an even more detailedembodiment, the coercivity of the PCD may be about 155 Oe to about 175Oe and the specific magnetic saturation of the PCD may be about 10G·cm³/g to about 15 G·cm³/g. The specific permeability (i.e., the ratioof specific magnetic saturation to coercivity) of the PCD may be about0.10 or less, such as about 0.060 to about 0.090. Despite the averagegrain size of the bonded diamond grains being less than about 30 μm insome embodiments, the metal-solvent catalyst content in the PCD may beless than about 7.5 wt % resulting in a desirable thermal stability.

In one embodiment, diamond particles having an average particle size ofabout 18 μm to about 20 μm are positioned adjacent to a cobalt-cementedtungsten carbide substrate and subjected to an HPHT process at atemperature of about 1390° C. to about 1430° C. and a pressure of about7.8 GPa to about 8.5 GPa. The PCD so-formed as a PCD table bonded to thesubstrate may exhibit a coercivity of about 155 Oe to about 175 Oe, aspecific magnetic saturation of about 10 G·cm³/g to about 15 G·cm³/g,and a cobalt content of about 5 wt % to about 7.5 wt %.

In one or more embodiments, a specific magnetic saturation constant forthe metal-solvent catalyst in the PCD may be about 185 G·cm³/g to about215 G·cm³/g. For example, the specific magnetic saturation constant forthe metal-solvent catalyst in the PCD may be about 195 G·cm³/g to about205 G·cm³/g. It is noted that the specific magnetic saturation constantfor the metal-solvent catalyst in the PCD may be composition dependent.

Generally, as the sintering pressure is increased above 7.5 GPa, a wearresistance of the PCD so-formed may increase. For example, the G_(ratio)may be at least about 4.0×10⁶, such as about 5.0×10⁶ to about 15.0×10⁶or, more particularly, about 8.0×10⁶ to about 15.0×10⁶. In someembodiments, the G_(ratio) may be at least about 30.0×10⁶. The G_(ratio)is the ratio of the volume of workpiece cut to the volume of PCD wornaway during the cutting process. An example of suitable parameters thatmay be used to determine a G_(ratio) of the PCD are a depth of cut forthe PCD cutting element of about 0.254 mm, a back rake angle for the PCDcutting element of about 20 degrees, an in-feed for the PCD cuttingelement of about 6.35 mm/rev, a rotary speed of the workpiece to be cutof about 101 rpm, and the workpiece may be made from Barre granitehaving a 914 mm outer diameter and a 254 mm inner diameter. During theG_(ratio) test, the workpiece is cooled with a coolant, such as water.

In addition to the aforementioned G_(ratio), despite the presence of themetal-solvent catalyst in the PCD, the PCD may exhibit a thermalstability that is close to, substantially the same as, or greater than apartially leached PCD material formed by sintering a substantiallysimilar diamond particle formulation at a lower sintering pressure(e.g., up to about 5.5 GPa) and in which the metal-solvent catalyst(e.g., cobalt) is leached therefrom to a depth of about 60 μm to about100 μm from a working surface thereof. The thermal stability of the PCDmay be evaluated by measuring the distance cut in a workpiece prior tocatastrophic failure, without using coolant, in a vertical lathe test(e.g., vertical turret lathe or a vertical boring mill). An example ofsuitable parameters that may be used to determine thermal stability ofthe PCD are a depth of cut for the PCD cutting element of about 1.27 mm,a back rake angle for the PCD cutting element of about 20 degrees, anin-feed for the PCD cutting element of about 1.524 mm/rev, a cuttingspeed of the workpiece to be cut of about 1.78 msec, and the workpiecemay be made from Barre granite having a 914 mm outer diameter and a 254mm inner diameter. In an embodiment, the distance cut in a workpieceprior to catastrophic failure as measured in the above-describedvertical lathe test may be at least about 1300 m, such as about 1300 mto about 3950 m.

PCD formed by sintering diamond particles having the same diamondparticle size distribution as a PCD embodiment of the invention, butsintered at a pressure of, for example, up to about 5.5 GPa and attemperatures in which diamond is stable may exhibit a coercivity ofabout 100 Oe or less and/or a specific magnetic saturation of about 16G·cm³/g or more. Thus, in one or more embodiments of the invention, PCDexhibits a metal-solvent catalyst content of less than 7.5 wt % and agreater amount of diamond-to-diamond bonding between diamond grains thanthat of a PCD sintered at a lower pressure, but with the same precursordiamond particle size distribution and catalyst.

It is currently believed by the inventors that forming the PCD bysintering diamond particles at a pressure of at least about 7.5 GPa maypromote nucleation and growth of diamond between the diamond particlesbeing sintered so that the volume of the interstitial regions of the PCDso-formed is decreased compared to the volume of interstitial regions ifthe same diamond particle distribution was sintered at a pressure of,for example, up to about 5.5 GPa and at temperatures where diamond isstable. For example, the diamond may nucleate and grow from carbonprovided by dissolved carbon in metal-solvent catalyst (e.g., liquefiedcobalt) infiltrating into the diamond particles being sintered,partially graphitized diamond particles, carbon from a substrate, carbonfrom another source (e.g., graphite particles and/or fullerenes mixedwith the diamond particles), or combinations of the foregoing. Thisnucleation and growth of diamond in combination with the sinteringpressure of at least about 7.5 GPa may contribute to the PCD so-formedhaving a metal-solvent catalyst content of less than about 7.5 wt %.

FIGS. 1A, 1B, and 2 schematically illustrate the manner in which thespecific magnetic saturation and the coercivity of the PCD may bedetermined using an apparatus, such as the KOERZIMAT CS 1.096instrument. FIG. 1A is a schematic diagram of an example of a magneticsaturation apparatus 100 configured to magnetize a PCD sample tosaturation. The magnetic saturation apparatus 100 includes a saturationmagnet 102 of sufficient strength to magnetize a PCD sample 104 tosaturation. The saturation magnet 102 may be a permanent magnet or anelectromagnet. In the illustrated embodiment, the saturation magnet 102is a permanent magnet that defines an air gap 106, and the PCD sample104 may be positioned on a sample holder 108 within the air gap 106.When the PCD sample 104 is lightweight, it may be secured to the sampleholder 108 using, for example, double-sided tape or other adhesive sothat the PCD sample 104 does not move responsive to the magnetic fieldfrom the saturation magnet 102 and the PCD sample 104 is magnetized atleast approximately to saturation.

Referring to the schematic diagram of FIG. 1B, after magnetizing the PCDsample 104 at least approximately to saturation using the magneticsaturation apparatus 100, a magnetic saturation of the PCD sample 104may be measured using a magnetic saturation measurement apparatus 120.The magnetic saturation measurement apparatus 120 includes a Helmholtzmeasuring coil 122 defining a passageway dimensioned so that themagnetized PCD sample 104 may be positioned therein on a sample holder124. Once positioned in the passageway, the sample holder 124 supportingthe magnetized PCD sample 104 may be moved axially along an axisdirection 126 to induce a current in the Helmholtz measuring coil 122.Measurement electronics 128 are coupled to the Helmholtz measuring coil122 and configured to calculate the magnetic saturation based upon themeasured current passing through the Helmholtz measuring coil 122. Themeasurement electronics 128 may also be configured to calculate a weightpercentage of magnetic material in the PCD sample 104 when thecomposition and magnetic characteristics of the metal-solvent catalystin the PCD sample 104 are known, such as with iron, nickel, cobalt, andalloys thereof. Specific magnetic saturation may be calculated basedupon the calculated magnetic saturation and the measured weight of thePCD sample 104.

The amount of metal-solvent catalyst in the PCD sample 104 may bedetermined using a number of different analytical techniques. Forexample, energy dispersive spectroscopy (e.g., EDAX), wavelengthdispersive x-ray spectroscopy (e.g., WDX), Rutherford backscatteringspectroscopy, or combinations thereof may be employed to determine theamount of metal-solvent catalyst in the PCD sample 104.

If desired, a specific magnetic saturation constant of the metal-solventcatalyst content in the PCD sample 104 may be determined using aniterative approach. A value for the specific magnetic saturationconstant of the metal-solvent catalyst in the PCD sample 104 may beiteratively chosen until a metal-solvent catalyst content calculated bythe analysis software of the KOERZIMAT CS 1.096 instrument using thechosen value substantially matches the metal-solvent catalyst contentdetermined via one or more analytical techniques, such as energydispersive spectroscopy, wavelength dispersive x-ray spectroscopy, orRutherford backscattering spectroscopy.

FIG. 2 is a schematic diagram of a coercivity measurement apparatus 200configured to determine a coercivity of a PCD sample. The coercivitymeasurement apparatus 200 includes a coil 202 and measurementelectronics 204 coupled to the coil 202. The measurement electronics 204are configured to pass a current through the coil 202 so that a magneticfield is generated. A sample holder 206 having a PCD sample 208 thereonmay be positioned within the coil 202. A magnetization sensor 210configured to measure a magnetization of the PCD sample 208 may becoupled to the measurement electronics 204 and positioned in proximityto the PCD sample 208.

During testing, the magnetic field generated by the coil 202 magnetizesthe PCD sample 208 at least approximately to saturation. Then, themeasurement electronics 204 apply a current so that the magnetic fieldgenerated by the coil 202 is increasingly reversed. The magnetizationsensor 210 measures a magnetization of the PCD sample 208 resulting fromapplication of the reversed magnetic field to the PCD sample 208. Themeasurement electronics 204 determine the coercivity of the PCD sample208, which is a measurement of the strength of the reversed magneticfield at which the magnetization of the PCD sample 208 is zero.

Embodiments of Methods for Fabricating PCD

The PCD may be formed by sintering a mass of a plurality of diamondparticles in the presence of a metal-solvent catalyst. The diamondparticles may exhibit an average particle size of about 50 μm or less,such as about 30 μm or less, about 20 μm or less, about 10 μm to about18 μm or, about 15 μm to about 18 μm. In some embodiments, the averageparticle size of the diamond particles may be about 10 μm or less, suchas about 2 μm to about 5 μm or submicron.

In an embodiment, the diamond particles of the mass of diamond particlesmay comprise a relatively larger size and at least one relativelysmaller size. As used herein, the phrases “relatively larger” and“relatively smaller” refer to particle sizes (by any suitable method)that differ by at least a factor of two (e.g., 30 μm and 15 μm).According to various embodiments, the mass of diamond particles mayinclude a portion exhibiting a relatively larger size (e.g., 30 μm, 20μm, 15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at leastone relatively smaller size (e.g., 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm,0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In one embodiment,the mass of diamond particles may include a portion exhibiting arelatively larger size between about 10 μm and about 40 μm and anotherportion exhibiting a relatively smaller size between about 1 μm and 4μm. In some embodiments, the mass of diamond particles may comprisethree or more different sizes (e.g., one relatively larger size and twoor more relatively smaller sizes), without limitation.

It is noted that the as-sintered diamond grain size may differ from theaverage particle size of the mass of diamond particles prior tosintering due to a variety of different physical processes, such asgrain growth, diamond particle fracturing, carbon provided from anothercarbon source (e.g., dissolved carbon in the metal-solvent catalyst), orcombinations of the foregoing. The metal-solvent catalyst (e.g., iron,nickel, cobalt, or alloys thereof) may be provided in particulate formmixed with the diamond particles, as a thin foil or plate placedadjacent to the mass of diamond particles, from a cemented carbidesubstrate including a metal-solvent catalyst, or combinations of theforegoing.

In order to efficiently sinter the mass of diamond particles, the massmay be enclosed in a pressure transmitting medium, such as a refractorymetal can, graphite structure, pyrophyllite, combinations thereof, orother suitable pressure transmitting structure to form a cell assembly.Examples of suitable gasket materials and cell structures for use inmanufacturing PCD are disclosed in U.S. Pat. No. 6,338,754 and U.S.patent application Ser. No. 11/545,929, each of which is incorporatedherein, in its entirety, by this reference. Another example of asuitable pressure transmitting material is pyrophyllite, which iscommercially available from Wonderstone Ltd. of South Africa. The cellassembly, including the pressure transmitting medium and mass of diamondparticles therein, is subjected to an HPHT process using an ultra-highpressure press at a temperature of at least about 1000° C. (e.g., about1100° C. to about 2200° C., or about 1200° C. to about 1450° C.) and apressure in the pressure transmitting medium of at least about 7.5 GPa(e.g., about 7.5 GPa to about 15 GPa, about 9 GPa to about 12 GPa, orabout 10 GPa to about 12.5 GPa) for a time sufficient to sinter thediamond particles together in the presence of the metal-solvent catalystand form the PCD comprising bonded diamond grains defining interstitialregions occupied by the metal-solvent catalyst. For example, thepressure in the pressure transmitting medium employed in the HPHTprocess may be at least about 8.0 GPa, at least about 9.0 GPa, at leastabout 10.0 GPa, at least about 11.0 GPa, at least about 12.0 GPa, or atleast about 14 GPa.

The pressure values employed in the HPHT processes disclosed hereinrefer to the pressure in the pressure transmitting medium at roomtemperature (e.g., about 25° C.) with application of pressure using anultra-high pressure press and not the pressure applied to exterior ofthe cell assembly. The actual pressure in the pressure transmittingmedium at sintering temperature may be slightly higher. The ultra-highpressure press may be calibrated at room temperature by embedding atleast one calibration material that changes structure at a knownpressure such as, PbTe, thallium, barium, or bismuth in the pressuretransmitting medium. Optionally, a change in resistance may be measuredacross the at least one calibration material due to a phase changethereof. For example, PbTe exhibits a phase change at room temperatureat about 6.0 GPa and bismuth exhibits a phase change at room temperatureat about 7.7 GPa. Examples of suitable pressure calibration techniquesare disclosed in G. Rousse, S. Klotz, A. M. Saitta, J.Rodriguez-Carvajal, M. I. McMahon, B. Couzinet, and M. Mezouar,“Structure of the Intermediate Phase of PbTe at High Pressure,” PhysicalReview B: Condensed Matter and Materials Physics, 71, 224116 (2005) andD. L. Decker, W. A. Bassett, L. Merrill, H. T. Hall, and J. D. Barnett,“High-Pressure Calibration: A Critical Review,” J. Phys. Chem. Ref.Data, 1, 3 (1972).

In an embodiment, a pressure of at least about 7.5 GPa in the pressuretransmitting medium may be generated by applying pressure to a cubichigh-pressure cell assembly that encloses the mass of diamond particlesto be sintered using anvils, with each anvil applying pressure to adifferent face of the cubic high-pressure assembly. In such anembodiment, a surface area of each anvil face of the anvils may beselectively dimensioned to facilitate application of pressure of atleast about 7.5 GPa to the mass of diamond particles being sintered. Forexample, the surface area of each anvil may be less than about 16.0 cm²,such as less than about 16.0 cm², about 8 cm² to about 10 cm². Theanvils may be made from a cobalt-cemented tungsten carbide or othermaterial having a sufficient compressive strength to help reduce damagethereto through repetitive use in a high-volume commercial manufacturingenvironment. As an alternative to or in addition to selectivelydimensioning the surface area of each anvil face, in an embodiment, twoor more internal anvils may be embedded in the cubic high-pressure cellassembly to further intensify pressure. For example, the article W.Utsumi, N. Toyama, S. Endo and F. E. Fujita, “X-ray diffraction underultrahigh pressure generated with sintered diamond anvils,” J. Appl.Phys., 60, 2201 (1986) is incorporated herein, in its entirety, by thisreference and discloses that sintered diamond anvils may be embedded ina cubic pressure transmitting medium for intensifying the pressureapplied by an ultra-high pressure press to a workpiece also embedded inthe cubic pressure transmitting medium.

PDC Embodiments and Methods of Fabricating PDCs

Referring to FIG. 3A, the PCD embodiments may be employed in a PDC forcutting applications, bearing applications, or many other applications.FIG. 3A is a cross-sectional view of an embodiment of a PDC 300. The PDC300 includes a substrate 302 bonded to a PCD table 304. The PCD table304 may be formed of PCD in accordance with any of the PCD embodimentsdisclosed herein. The PCD table 304 exhibits at least one workingsurface 306 and at least one lateral dimension “D” (e.g., a diameter).Although FIG. 3A shows the working surface 306 as substantially planar,the working surface 306 may be concave, convex, or another nonplanargeometry. Furthermore, other regions of the PCD table 304 may functionas a working region, such as a peripheral side surface and/or an edge.The substrate 302 may be generally cylindrical or another selectedconfiguration, without limitation. Although FIG. 3A shows an interfacialsurface 308 of the substrate 302 as being substantially planar, theinterfacial surface 308 may exhibit a selected nonplanar topography,such as a grooved, ridged, or other nonplanar interfacial surface. Thesubstrate 302 may include, without limitation, cemented carbides, suchas tungsten carbide, titanium carbide, chromium carbide, niobiumcarbide, tantalum carbide, vanadium carbide, or combinations thereofcemented with iron, nickel, cobalt, or alloys thereof. For example, inone embodiment, the substrate 302 comprises cobalt-cemented tungstencarbide.

In some embodiments, the PCD table 304 may include two or more layeredregions 310 and 312 exhibiting different compositions and/or differentaverage diamond grain sizes. For example, the region 310 is locatedadjacent to the interface surface 308 of the substrate 302 and exhibitsa first diamond grain size, while the region 312 is remote from thesubstrate 302 and exhibits a second average diamond grain size that isless than that of the first average diamond grain size. For example, thesecond average diamond grain size may be about 90% to about 98% (e.g.,about 90 to about 95%) of the first diamond grain size. In anotherembodiment, the second average diamond grain size may be greater thanthat of the first average diamond grain size. For example, the firstaverage diamond grain size may be about 90% to about 98% (e.g., about 90to about 95%) of the second diamond grain size.

As an alternative to or in addition to the first and second regionsexhibiting different diamond grain sizes, in an embodiment, thecomposition of the region 310 may be different than that of the region312. The region 310 may include about 15 wt % or less of atungsten-containing material (e.g., tungsten and/or tungsten carbide)interspersed between the diamond grains to improve toughness, while theregion 312 may be substantially free of tungsten. For example, thetungsten-containing material may be present in the region 310 in anamount of about 1 wt % to about 10 wt %, about 5 wt % to about 10 wt %,or about 10 wt %.

FIG. 3B is a schematic illustration of an embodiment of a method forfabricating the PDC 300 shown in FIG. 3A. Referring to FIG. 3B, a massof diamond particles 305 having any of the above-mentioned averageparticle sizes and distributions (e.g., an average particle size ofabout 50 μm or less) is positioned adjacent to the interfacial surface308 of the substrate 302. As previously discussed, the substrate 302 mayinclude a metal-solvent catalyst. The mass of diamond particles 305 andsubstrate 302 may be subjected to an HPHT process using any of theconditions previously described with respect to sintering the PCDembodiments disclosed herein. The PDC 300 so-formed includes the PCDtable 304 that comprises PCD, formed of any of the PCD embodimentsdisclosed herein, integrally formed with the substrate 302 and bonded tothe interfacial surface 308 of the substrate 302. If the substrate 302includes a metal-solvent catalyst, the metal-solvent catalyst mayliquefy and infiltrate the mass of diamond particles 305 to promotegrowth between adjacent diamond particles of the mass of diamondparticles 305 to form the PCD table 304 comprised of a body of bondeddiamond grains having the infiltrated metal-solvent catalystinterstitially disposed between bonded diamond grains. For example, ifthe substrate 302 is a cobalt-cemented tungsten carbide substrate,cobalt from the substrate 302 may be liquefied and infiltrate the massof diamond particles 305 to catalyze formation of the PCD table 304.

In some embodiments, the mass of diamond particles 305 may include twoor more layers exhibiting different compositions and/or differentaverage diamond particle sizes. For example, a first layer may belocated adjacent to the interface surface 308 of the substrate 302 andexhibit a first diamond particle size, while a second layer may belocated remote from the substrate 302 and exhibit a second averagediamond particle size that is less than that of the first averagediamond particle size. For example, the second average diamond particlesize may be about 90% to about 98% (e.g., about 90 to about 95%) of thefirst diamond particle size. In another embodiment, the second averagediamond particle size may be greater than that of the first averagediamond particle size. For example, the first average diamond particlesize may be about 90% to about 98% (e.g., about 90 to about 95%) of thesecond diamond particle size.

As an alternative to or in addition to the first and second layersexhibiting different diamond particles sizes, in an embodiment, thecomposition of the first layer may be different than that of the secondlayer. The first layer may include about 15 wt % or less of atungsten-containing material (e.g., tungsten and/or tungsten carbide)mixed with the diamond particles, while the second layer may besubstantially free of tungsten. For example, the tungsten-containingmaterial may be present in the first layer in an amount of about 1 wt %to about 10 wt %, about 5 wt % to about 10 wt %, or about 10 wt %.

Employing selectively dimensioned anvil faces and/or internal anvils inthe ultra-high pressure press used to process the mass of diamondparticles 305 and substrate 302 enables forming the at least one lateraldimension d of the PCD table 304 to be about 0.80 cm or more. Referringagain to FIG. 3A, for example, the at least one lateral dimension “D”may be about 0.80 cm to about 3.0 cm and, in some embodiments, about 1.3cm to about 1.9 cm or about 1.6 cm to about 1.9 cm. A representativevolume of the PCD table 304 (or any PCD article of manufacture disclosedherein) formed using the selectively dimensioned anvil faces and/orinternal anvils may be at least about 0.050 cm³. For example, the volumemay be about 0.25 cm³ to at least about 1.25 cm³ or about 0.1 cm³ to atleast about 0.70 cm³. A representative volume for the PDC 300 may beabout 0.4 cm³ to at least about 4.6 cm³, such as about 1.1 cm³ to atleast about 2.3 cm³.

In other embodiments, a PCD table according to an embodiment may beseparately formed using an HPHT sintering process (i.e., a pre-sinteredPCD table) and, subsequently, bonded to the interfacial surface 308 ofthe substrate 302 by brazing, using a separate HPHT bonding process, orany other suitable joining technique, without limitation. In yet anotherembodiment, a substrate may be formed by depositing a binderless carbide(e.g., tungsten carbide) via chemical vapor deposition onto theseparately formed PCD table.

In any of the embodiments disclosed herein, substantially all or aselected portion of the metal-solvent catalyst may be removed (e.g., vialeaching) from the PCD table. In an embodiment, metal-solvent catalystin the PCD table may be removed to a selected depth from at least oneexterior working surface (e.g., the working surface 306 and/or asidewall working surface of the PCD table 304) so that only a portion ofthe interstitial regions are occupied by metal-solvent catalyst. Forexample, substantially all or a selected portion of the metal-solventcatalyst may be removed from the PCD table 304 of the PDC 300 to aselected depth from the working surface 306.

In another embodiment, a PCD table may be fabricated according to any ofthe disclosed embodiments in a first HPHT process, leached to removesubstantially all of the metal-solvent catalyst from the interstitialregions between the bonded diamond grains, and subsequently bonded to asubstrate in a second HPHT process. In the second HPHT process, aninfiltrant from, for example, a cemented carbide substrate mayinfiltrate into the interstitial regions from which the metal-solventcatalyst was depleted. For example, the infiltrant may be cobalt that isswept-in from a cobalt-cemented tungsten carbide substrate. In oneembodiment, the first and/or second HPHT process may be performed at apressure of at least about 7.5 GPa. In one embodiment, the infiltrantmay be leached from the infiltrated PCD table using a second acidleaching process following the second HPHT process.

In some embodiments, the pressure employed in the HPHT process used tofabricate the PDC 300 may be sufficient to reduce residual stresses inthe PCD table 304 that develop during the HPHT process due to thethermal expansion mismatch between the substrate 302 and the PCD table304. In such an embodiment, the principal stress measured on the workingsurface 306 of the PDC 300 may exhibit a value of about −345 MPa toabout 0 MPa, such as about −289 MPa. For example, the principal stressmeasured on the working surface 306 may exhibit a value of about −345MPa to about 0 MPa. A conventional PDC fabricated using an HPHT processat a pressure below about 7.5 GPa may result in a PCD table thereofexhibiting a principal stress on a working surface thereof of about−1724 MPa to about −414 MPa, such as about −770 MPa.

Residual stress may be measured on the working surface 306 of the PCDtable 304 of the PDC 300 as described in T. P. Lin, M. Hood, G. A.Cooper, and R. H. Smith, “Residual stresses in polycrystalline diamondcompacts,” J. Am. Ceram. Soc. 77, 6, 1562-1568 (1994). Moreparticularly, residual strain may be measured with a rosette strain gagebonded to the working surface 306. Such strain may be measured fordifferent levels of removal of the substrate 302 (e.g., as material isremoved from the back of the substrate 302). Residual stress may becalculated from the measured residual strain data.

FIG. 3C is a graph of residual principal stress versus substratethickness that was measured in a PCD table of a PDC fabricated atpressure above about 7.5 GPa in accordance with an embodiment of theinvention and a PCD table of a conventionally formed PDC. The substrateof each PDC had a substantially planar interfacial surface. The residualprincipal stress was determined using the technique described in thearticle referenced above by Lin et al. Curve 310 shows the measuredresidual principal stress on a working surface of the PDC fabricated ata pressure above about 7.5 GPa. The PDC that was fabricated at apressure above about 7.5 GPa had a PCD table thickness dimension ofabout 1 mm and the substrate had a thickness dimension of about 7 mm anda diameter of about 13 mm. Curve 312 shows the measured residualprincipal stress on a working surface of a PCD table of a conventionallyPDC fabricated at pressure below about 7.5 GPa. The PDC that wasfabricated at a pressure below about 7.5 GPa had a PCD table thicknessdimension of about 1 mm and the substrate had a thickness dimension ofabout 7 mm and a diameter of about 13 mm. The highest absolute value ofthe residual principal stress occurs with the full substrate length ofabout 7 mm. As shown by the curves 310 and 312, increasing the pressureemployed in the HPHT process used to fabricate a PDC, above about 7.5GPa may reduce the highest absolute value of the principal residualstress in a PCD table thereof by about 60% relative to a conventionallyfabricated PDC. For example, at the full substrate length, the absolutevalue of the principal residual stress in the PCD table fabricated at apressure above about 7.5 GPa is about 60% less than the absolute valueof the principal residual stress in the PCD table of the conventionallyfabricated PDC.

As discussed above in relation to FIG. 3C, the application of higherpressure in the HPHT process used to fabricate a PDC may substantiallyreduce the residual compressive stresses in the PCD table. Typically,high residual compressive stresses in the PCD table are believeddesirable to help reduce crack propagation in the PCD table. Theinventors have found that the reduced residual compressive stresses in aPCD table of a PDC fabricated in an HPHT process at a pressure of atleast about 7.5 GPa may result in detrimental cracking in the PCD tableand de-bonding of the PCD table from the substrate upon brazing thesubstrate to, for example, a carbide extension and/or a bit body of arotary drill bit depending upon the extent of the nonplanarity of theinterfacial surface of the substrate. It is believed by the inventorsthat when the PDC is fabricated at a pressure of at least about 7.5 GPa,at the brazing temperature, tensile stresses generated in the PCD tabledue to thermal expansion are greater than if the PCD table had higherresidual compressive stresses. Due to the higher tensile stresses at thebrazing temperature, hoop stresses generated in the PCD by nonplanarsurface features (e.g., protrusions) of the substrate may cause the PCDtable to form radially-extending and vertically-extending cracks and/orde-bond from the substrate more frequently than if fabricated atrelatively lower pressures. Typically, conventional wisdom taught that ahighly nonplanar interfacial surface for the substrate helped preventde-bonding of the PCD table from the substrate. Thus, in certainembodiments discussed in more detail in FIGS. 3A-6B, the inventors haveproceeded contrary to conventional wisdom, which suggested that a highlynonplanar interfacial surface for the substrate promotes bonding. Insuch embodiments, the topography of the interfacial surface of thesubstrate may be controlled so that it is still substantially planar andexhibits a nonplanarity that does not exceed a maximum threshold.

Referring again to FIG. 3A, in an embodiment, the interfacial surface308 of the substrate 302 may be substantially planar. For example, tothe extent that the interfacial surface 308 includes a plurality ofprotrusions, the protrusions may exhibit an average surface reliefheight of about 0 to less than about 0.00010 inch, about 0 to about0.00050 inch, about 0 to about 0.00075 inch, or about 0.000010 inch toabout 0.00010 inch. The average surface relief is the height that theprotrusions extend above the lowest point of the interfacial surface308. A ratio of a surface area of the interfacial surface in the absenceof the plurality of protrusions (i.e., a flat interfacial surface) to asurface area of the interfacial surface with the plurality ofprotrusions is greater than about 0.600. An example of an interfacialsurface that is substantially planar is one in which the ratio isgreater than about 0.600. For example, the ratio may be about 0.600 toabout 0.650, about 0.650 to about 0.725, about 0.650 to about 0.750,about 0.650 to about 0.950, about 0.750 to less than 1.0, or about 0.750to about 1.0.

FIGS. 4A-6B illustrate embodiments in which the selected substantiallyplanar topography of the interfacial surface of the substrate iscontrolled to reduce or substantially eliminate cracking in and/orde-bonding of a PCD table of a PDC. FIGS. 4A and 4B are explodedisometric and assembled isometric views, respectively, of an embodimentof a PDC 400 comprising a substrate 402 including an interfacial surface404 exhibiting a selected substantially planar topography. The substrate402 may be made from the same carbide materials as the substrate 302shown in FIG. 3A. The interfacial surface 404 includes a plurality ofprotrusions 406 spaced from each other and extending substantiallytransversely to the length of the substrate 402. The protrusions 406define a plurality of grooves 408 between pairs of the protrusions 406.A PCD table 410 may be bonded to the interfacial surface 406. The PCDtable 410 may exhibit some or all of the magnetic, mechanical, thermalstability, wear resistance, size, compositional, diamond-to-diamondbonding, or grain size properties of the PCD disclosed herein and/or thePCD table 304 shown in FIG. 3A. The PCD table 410 exhibits a maximumthickness “T.” Because the PCD table 410 may be integrally formed withthe substrate 402 and fabricated from precursor diamond particles, thePCD table 410 may have an interfacial surface 411 that is configured tocorrespond to the topography of the interfacial surface 404 of thesubstrate 402.

A ratio of a surface area of the interfacial surface 404 in the absenceof the plurality of protrusions 406 (i.e., a flat interfacial surface)to a surface area of the interfacial surface with the protrusions 406 isgreater than about 0.600. For example, the ratio may be about 0.600 toabout 0.650, about 0.650 to about 0.725, about 0.650 to about 0.750,about 0.650 to about 0.950, about 0.750 to less than 1.0, or about 0.750to about 1.0.

The plurality of protrusions 406 exhibits an average surface reliefheight “h,” which is the average height that the protrusions 406 extendabove the lowest point of the interfacial surface 404. For example, hmay be greater than 0 to less than about 0.030 inch, greater than 0 toabout 0.020 inch, greater than 0 to about 0.015 inch, about 0.0050 inchto about 0.010 inch, or 0.0080 inch to about 0.010 inch. The maximumthickness “T” may be about 0.050 inch to about 0.20 inch, such as about0.050 inch to about 0.16 inch, about 0.050 inch to about 0.10 inch,about 0.050 inch to about 0.085 inch or about 0.070 inch to about 0.080inch. The ratio of h/T may be less than about 0.25, such as about 0.050to about 0.125, about 0.050 to about 0.10, about 0.070 to about 0.090,or about 0.050 to about 0.075.

Referring to FIG. 4B, the outermost of the protrusions 406 (indicated as406 a and 406 b) may be laterally spaced from an exterior peripheralsurface 414 of the substrate 402 by a distance d. When the PDC 400 issubstantially cylindrical, a ratio of d to the radius of the PCD table“R” may be about 0.030 to about 1.0, about 0.035 to about 0.080, orabout 0.038 to about 0.060.

FIG. 5A is cross-sectional view of a PDC 500 comprising a substrate 502including an interfacial surface 504 exhibiting a selected substantiallyplanar topography according to yet another embodiment and FIG. 5B is anisometric view of the substrate 502. The substrate 502 may be made fromthe same carbide materials as the substrate 302 shown in FIG. 3A. Theinterfacial surface 504 of the substrate 502 includes a plurality ofhexagonal protrusions 506 that extend outwardly from a face 508. Theface 508 may be convex, as in the illustrated embodiment, orsubstantially planar. Tops 509 of the protrusions 506 may lie generallyin a common plane. The plurality of protrusions 506 defines a pluralityof internal cavities 510. A depth of each internal cavity 510 maydecrease as they approach the center of the substrate 502. A bottom 511of each cavity 510 may follow the profile of the face 508.

The PDC 500 further includes a PCD table 512 exhibiting a maximumthickness “T,” which is bonded to the interfacial surface 504 of thesubstrate 502. The thickness of the PCD table 512 gradually increaseswith lateral distance from the center of the PCD table 512 toward aperimeter 513 of the PDC 500. The PCD table 512 may be configured tocorrespond to the topography of the interfacial surface 504 of thesubstrate 502. For example, protrusions 513 of the PCD table 512 mayfill each of the internal cavities 510 defined by the protrusions 506 ofthe substrate 502. The PCD table 512 may exhibit some or all of themagnetic, mechanical, thermal stability, wear resistance, size,compositional, diamond-to-diamond bonding, or grain size properties ofthe PCD disclosed herein and/or the PCD table 304 shown in FIG. 3A. Theclosed features of the hexagonal protrusions 506 include a draft angleα, such as about 5 degrees to about 15 degrees.

A ratio of a surface area of the interfacial surface 504 in the absenceof the protrusions 506 (i.e., a flat interfacial surface) to a surfacearea of the interfacial surface with the protrusions 506 is greater thanabout 0.600. For example, the ratio may be about 0.600 to about 0.650,about 0.650 to about 0.725, about 0.650 to about 0.750, about 0.650 toabout 0.950, about 0.750 to less than 1.0, or about 0.750 to about 1.0.

The plurality of protrusions 506 exhibits an average surface reliefheight “h,” which is the average height that the protrusions 506 extendabove the lowest point of the interfacial surface 504. For example, hmay be greater than 0 to less than about 0.030 inch, greater than 0 toabout 0.020 inch, greater than 0 to about 0.015 inch, about 0.0050 inchto about 0.010 inch, or 0.0080 inch to about 0.010 inch. The maximumthickness “T” may be about 0.050 inch to about 0.10 inch, such as about0.050 inch to about 0.085 inch or about 0.070 inch to about 0.080 inch.The ratio of h/T may be less than about 0.25, such as about 0.050 toabout 0.125, about 0.050 to about 0.10, about 0.070 to about 0.090, orabout 0.050 to about 0.075.

It is noted that the interfacial surface geometries shown in the PDCs400 and 500 are merely two examples of suitable interfacial surfacegeometries. Other interfacial surface geometries may be employed thatdepart from the illustrated interfacial surface geometries shown in thePDCs 400 and 500 of FIGS. 4A-5B.

Working Examples

The following working examples provide further detail about the magneticproperties of PCD tables of PDCs fabricated in accordance with theprinciples of some of the specific embodiments of the invention. Themagnetic properties of each PCD table listed in Tables I-IV were testedusing a KOERZIMAT CS 1.096 instrument that is commercially availablefrom Foerster Instruments of Pittsburgh, Pa. The specific magneticsaturation of each PCD table was measured in accordance with ASTMB886-03 (2008) and the coercivity of each PCD table was measured usingASTM B887-03 (2008) e1 using a KOERZIMAT CS 1.096 instrument. The amountof cobalt-based metal-solvent catalyst in the tested PCD tables wasdetermined using energy dispersive spectroscopy and Rutherfordbackscattering spectroscopy. The specific magnetic saturation constantof the cobalt-based metal-solvent catalyst in the tested PCD tables wasdetermined to be about 201 G·cm³/g using an iterative analysis aspreviously described. When a value of 201 G·cm³/g was used for thespecific magnetic saturation constant of the cobalt-based metal-solventcatalyst, the calculated amount of the cobalt-based metal-solventcatalyst in the tested PCD tables using the analysis software of theKOERZIMAT CS 1.096 instrument substantially matched the measurementsusing energy dispersive spectroscopy and Rutherford spectroscopy.

Table I below lists PCD tables that were fabricated in accordance withthe principles of certain embodiments of the invention discussed above.Each PCD table was fabricated by placing a mass of diamond particleshaving the listed average diamond particle size adjacent to acobalt-cemented tungsten carbide substrate in a niobium container,placing the container in a high-pressure cell medium, and subjecting thehigh-pressure cell medium and the container therein to an HPHT processusing an HPHT cubic press to form a PCD table bonded to the substrate.The surface area of each anvil of the HPHT press and the hydraulic linepressure used to drive the anvils were selected so that the sinteringpressure was at least about 7.8 GPa. The temperature of the HPHT processwas about 1400° C. and the sintering pressure was at least about 7.8GPa. The sintering pressures listed in Table I refer to the pressure inthe high-pressure cell medium at room temperature, and the actualsintering pressures at the sintering temperature are believed to begreater. After the HPHT process, the PCD table was removed from thesubstrate by grinding away the substrate. However, the substrate mayalso be removed using electro-discharge machining or another suitablemethod.

TABLE I Selected Magnetic Properties of PCD Tables Fabricated Accordingto Embodiments of the Invention. Average Specific Diamond SinteringMagnetic Specific Particle Size Pressure Saturation CalculatedCoercivity Permeability Example (μm) (GPa) (G · cm³/g) Co wt % (Oe) (G ·cm³/g · Oe) 1 20 7.8 11.15 5.549 130.2 0.08564 2 19 7.8 11.64 5.792170.0 0.06847 3 19 7.8 11.85 5.899 157.9 0.07505 4 19 7.8 11.15 5.550170.9 0.06524 5 19 7.8 11.43 5.689 163.6 0.06987 6 19 7.8 10.67 5.150146.9 0.07263 7 19 7.8 10.76 5.357 152.3 0.07065 8 19 7.8 10.22 5.087145.2 0.07039 9 19 7.8 10.12 5.041 156.6 0.06462 10 19 7.8 10.72 5.549137.1 0.07819 11 11 7.8 12.52 6.229 135.3 0.09254 12 11 7.8 12.78 6.362130.5 0.09793 13 11 7.8 12.69 6.315 134.6 0.09428 14 11 7.8 13.20 6.569131.6 0.1003

Table II below lists conventional PCD tables that were fabricated. EachPCD table listed in Table II was fabricated by placing a mass of diamondparticles having the listed average diamond particle size adjacent to acobalt-cemented tungsten carbide substrate in a niobium container,placing container in a high-pressure cell medium, and subjecting thehigh-pressure cell medium and the container therein to an HPHT processusing an HPHT cubic press to form a PCD table bonded to the substrate.The surface area of each anvil of the HPHT press and the hydraulic linepressure used to drive the anvils were selected so that the sinteringpressure was about 4.6 GPa. Except for samples 15, 16, 18, and 19, whichwere subjected to a temperature of about 1430° C., the temperature ofthe HPHT process was about 1400° C. and the sintering pressure was about4.6 GPa. The sintering pressures listed in Table II refer to thepressure in the high-pressure cell medium at room temperature. After theHPHT process, the PCD table was removed from the cobalt-cementedtungsten carbide substrate by grinding away the cobalt-cemented tungstencarbide substrate.

TABLE II Selected Magnetic Properties of Several Conventional PCDTables. Specific Average Sintering Magnetic Specific Diamond PressureSaturation Calculated Coercivity Permeability Example Particle Size (μm)(GPa) (G · cm³/g) Co wt % (Oe) (G · cm³/g · Oe) 15 20 4.61 19.30 9.60594.64 0.2039 16 20 4.61 19.52 9.712 96.75 0.2018 17 20 4.61 19.87 9.88994.60 0.2100 18 20 5.08 18.61 9.260 94.94 0.1960 19 20 5.08 18.21 9.061100.4 0.1814 20 20 5.86 16.97 8.452 108.3 0.1567 21 20 4.61 17.17 8.543102.0 0.1683 22 20 4.61 17.57 8.745 104.9 0.1675 23 20 5.08 16.10 8.014111.2 0.1448 24 20 5.08 16.79 8.357 107.1 0.1568

As shown in Tables I and II, the conventional PCD tables listed in TableII exhibit a higher cobalt content therein than the PCD tables listed inTable I as indicated by the relatively higher specific magneticsaturation values. Additionally, the conventional PCD tables listed inTable II exhibit a lower coercivity indicative of a relatively greatermean free path between diamond grains, and thus may indicate relativelyless diamond-to-diamond bonding between the diamond grains. Thus, thePCD tables according to examples of the invention listed in Table I mayexhibit significantly less cobalt therein and a lower mean free pathbetween diamond grains than the PCD tables listed in Table II.

Table III below lists conventional PCD tables that were obtained fromPDCs. Each PCD table listed in Table III was separated from acobalt-cemented tungsten carbide substrate bonded thereto by grinding.

TABLE III Selected Magnetic Properties of Several Conventional PCDTables. Specific Magnetic Specific Saturation Calculated CoercivityPermeability Example (G · cm³/g) Co wt % (Oe) (G · cm³/g · Oe) 25 17.238.572 140.4 0.1227 26 16.06 7.991 150.2 0.1069 27 15.19 7.560 146.10.1040 28 17.30 8.610 143.2 0.1208 29 17.13 8.523 152.1 0.1126 30 17.008.458 142.5 0.1193 31 17.08 8.498 147.2 0.1160 32 16.10 8.011 144.10.1117

Table IV below lists conventional PCD tables that were obtained fromPDCs. Each PCD table listed in Table IV was separated from acobalt-cemented tungsten carbide substrate bonded thereto by grindingthe substrate away. Each PCD table listed in Table IV and tested had aleached region from which cobalt was depleted and an unleached region inwhich cobalt is interstitially disposed between bonded diamond grains.The leached region was not removed. However, to determine the specificmagnetic saturation and the coercivity of the unleached region of thePCD table having metal-solvent catalyst occupying interstitial regionstherein, the leached region may be ground away so that only theunleached region of the PCD table remains. It is expected that theleached region causes the specific magnetic saturation to be lower andthe coercivity to be higher than if the leached region was removed andthe unleached region was tested.

TABLE IV Selected Magnetic Properties of Several Conventional LeachedPCD Tables. Specific Specific Magnetic Permeability SaturationCalculated Coercivity (G · cm³ Example (G · cm³ per gram) Co wt % (Oe)per g · Oe) 33 17.12 8.471 143.8 0.1191 34 13.62 6.777 137.3 0.09920 3515.87 7.897 140.1 0.1133 36 12.95 6.443 145.5 0.0890 37 13.89 6.914142.0 0.09782 38 13.96 6.946 146.9 0.09503 39 13.67 6.863 133.8 0.102240 12.80 6.369 146.3 0.08749

As shown in Tables I, III, and IV, the conventional PCD tables of TablesIII and IV exhibit a higher cobalt content therein than the PCD tableslisted in Table I as indicated by the relatively higher specificmagnetic saturation values. This is believed by the inventors to be aresult of the PCD tables listed in Tables III and IV being formed bysintering diamond particles having a relatively greater percentage offine diamond particles than the diamond particle formulations used tofabricate the PCD tables listed in Table I.

Examples 41-120 tested four different substrate interfacial surfacegeometries to evaluate the effect of the interfacial surface area of thesubstrate. Twenty samples of each substrate interfacial surface geometrywere tested. All of the PDCs in examples 41-120 were fabricated byplacing a mass of diamond particles having an average diamond particlesize of about 19 μm adjacent to a cobalt-cemented tungsten carbidesubstrate in a niobium container, placing the container in ahigh-pressure cell medium, and subjecting the high-pressure cell mediumand the container therein to an HPHT process using an HPHT cubic pressto form a PCD table bonded to the substrate. The surface area of eachanvil of the HPHT press and the hydraulic line pressure used to drivethe anvils were selected so that the sintering pressure was at leastabout 7.7 GPa. The temperature of the HPHT process was about 1400° C.The sintering pressure of 7.7 GPa refers to the pressure in thehigh-pressure cell medium at room temperature, and the actual sinteringpressure at the sintering temperature of about 1400° C. is believed tobe greater.

The interfacial surface for the substrate in the PDCs of examples 41-60was a substantially planar interfacial surface having essentially nosurface topography other than surface roughness. The interfacial surfacefor the substrate in the PDCs of examples 61-80 was similar to theinterfacial surface 404 shown in FIG. 4A. The interfacial surface forthe substrate in the PDCs of Examples 81-100 was slightly convex with aplurality of radially and circumferentially equally-spaced cylindricalprotrusions. The interfacial surface for the substrate in the PDCs ofexamples 101-120 was similar to the interfacial surface 504 shown inFIGS. 5A and 5B.

After fabricating the PDCs of examples 41-120, the substrate of each PDCwas brazed to an extension cobalt-cemented tungsten carbide substrate.The braze alloy had a composition of about 25 wt % Au, about 10 wt % Ni,about 15 wt % Pd, about 13 wt % Mn, and about 37 wt % Cu. The brazingprocess was performed at a brazing temperature of about 1013° C. Afterthe brazing process, the PDCs of examples 41-120 were individuallyexamined using an optical microscope to determine if cracks were presentin the PCD tables.

Table V below lists the substrate diameter, surface area of theinterfacial surface of the substrates for each type of substrategeometry, the ratio of the interfacial surface area of the substrate toa flat interfacial surface of a substrate with the same diameter, andthe number of PDC samples in which the PCD table cracked upon brazing tothe extension cobalt-cemented tungsten carbide substrate. As shown inTable V, as the surface area of the interfacial surface of the substratedecreases, the prevalence of the PCD table cracking decreases uponbrazing.

TABLE V Effect of Substrate Interfacial Surface Area on PCD TableCracking Upon Brazing Number of Interfacial Surface Samples ThatSubstrate Area of Substrate Cracked When Example Diameter (in) (in²)Ratio Brazed 41-60 0.625 0.308 1.0 0 61-80 0.625 0.398 0.772 0  81-1000.625 0.524 0.588 2 out of 20 101-120 0.625 0.585 0.526 9 out of 20

Embodiments of Applications for PCD and PDCs

The disclosed PCD and PDC embodiments may be used in a number ofdifferent applications including, but not limited to, use in a rotarydrill bit (FIGS. 6A and 6B), a thrust-bearing apparatus (FIG. 7), aradial bearing apparatus (FIG. 8), a subterranean drilling system (FIG.9), and a wire-drawing die (FIG. 10). The various applications discussedabove are merely some examples of applications in which the PCD and PDCembodiments may be used. Other applications are contemplated, such asemploying the disclosed PCD and PDC embodiments in friction stir weldingtools.

FIG. 6A is an isometric view and FIG. 6B is a top elevation view of anembodiment of a rotary drill bit 600. The rotary drill bit 600 includesat least one PDC configured according to any of the previously describedPDC embodiments. The rotary drill bit 600 comprises a bit body 602 thatincludes radially and longitudinally extending blades 604 with leadingfaces 606, and a threaded pin connection 608 for connecting the bit body602 to a drilling string. The bit body 602 defines a leading endstructure for drilling into a subterranean formation by rotation about alongitudinal axis 610 and application of weight-on-bit. At least one PDCcutting element, configured according to any of the previously describedPDC embodiments (e.g., the PDC 300 shown in FIG. 3A), may be affixed tothe bit body 602. With reference to FIG. 6B, a plurality of PDCs 612 aresecured to the blades 604. For example, each PDC 612 may include a PCDtable 614 bonded to a substrate 616. More generally, the PDCs 612 maycomprise any PDC disclosed herein, without limitation. In addition, ifdesired, in some embodiments, a number of the PDCs 612 may beconventional in construction. Also, circumferentially adjacent blades604 define so-called junk slots 618 therebetween, as known in the art.Additionally, the rotary drill bit 600 may include a plurality of nozzlecavities 620 for communicating drilling fluid from the interior of therotary drill bit 600 to the PDCs 612.

FIGS. 6A and 6B merely depict an embodiment of a rotary drill bit thatemploys at least one cutting element comprising a PDC fabricated andstructured in accordance with the disclosed embodiments, withoutlimitation. The rotary drill bit 600 is used to represent any number ofearth-boring tools or drilling tools, including, for example, core bits,roller-cone bits, fixed-cutter bits, eccentric bits, bicenter bits,reamers, reamer wings, or any other downhole tool including PDCs,without limitation.

The PCD and/or PDCs disclosed herein (e.g., the PDC 300 shown in FIG.3A) may also be utilized in applications other than rotary drill bits.For example, the disclosed PDC embodiments may be used in thrust-bearingassemblies, radial bearing assemblies, wire-drawing dies, artificialjoints, machining elements, and heat sinks.

FIG. 7 is an isometric cutaway view of an embodiment of a thrust-bearingapparatus 700, which may utilize any of the disclosed PDC embodiments asbearing elements. The thrust-bearing apparatus 700 includes respectivethrust-bearing assemblies 702. Each thrust-bearing assembly 702 includesan annular support ring 704 that may be fabricated from a material, suchas carbon steel, stainless steel, or another suitable material. Eachsupport ring 704 includes a plurality of recesses (not labeled) thatreceive a corresponding bearing element 706. Each bearing element 706may be mounted to a corresponding support ring 704 within acorresponding recess by brazing, press-fitting, using fasteners, oranother suitable mounting technique. One or more, or all of bearingelements 706 may be configured according to any of the disclosed PDCembodiments. For example, each bearing element 706 may include asubstrate 708 and a PCD table 710, with the PCD table 710 including abearing surface 712.

In use, the bearing surfaces 712 of one of the thrust-bearing assemblies702 bear against the opposing bearing surfaces 712 of the other one ofthe bearing assemblies 702. For example, one of the thrust-bearingassemblies 702 may be operably coupled to a shaft to rotate therewithand may be termed a “rotor.” The other one of the thrust-bearingassemblies 702 may be held stationary and may be termed a “stator.”

FIG. 8 is an isometric cutaway view of an embodiment of a radial bearingapparatus 800, which may utilize any of the disclosed PDC embodiments asbearing elements. The radial bearing apparatus 800 includes an innerrace 802 positioned generally within an outer race 804. The outer race804 includes a plurality of bearing elements 806 affixed thereto thathave respective bearing surfaces 808. The inner race 802 also includes aplurality of bearing elements 810 affixed thereto that have respectivebearing surfaces 812. One or more, or all of the bearing elements 806and 810 may be configured according to any of the PDC embodimentsdisclosed herein. The inner race 802 is positioned generally within theouter race 804 and, thus, the inner race 802 and outer race 804 may beconfigured so that the bearing surfaces 808 and 812 may at leastpartially contact one another and move relative to each other as theinner race 802 and outer race 804 rotate relative to each other duringuse.

The radial bearing apparatus 800 may be employed in a variety ofmechanical applications. For example, so-called “roller cone” rotarydrill bits may benefit from a radial bearing apparatus disclosed herein.More specifically, the inner race 802 may be mounted to a spindle of aroller cone and the outer race 804 may be mounted to an inner boreformed within a cone and that such an outer race 804 and inner race 802may be assembled to form a radial bearing apparatus.

Referring to FIG. 9, the thrust-bearing apparatus 700 and/or radialbearing apparatus 800 may be incorporated in a subterranean drillingsystem. FIG. 9 is a schematic isometric cutaway view of a subterraneandrilling system 900 that includes at least one of the thrust-bearingapparatuses 700 shown in FIG. 7 according to another embodiment. Thesubterranean drilling system 900 includes a housing 902 enclosing adownhole drilling motor 904 (i.e., a motor, turbine, or any other devicecapable of rotating an output shaft) that is operably connected to anoutput shaft 906. A first thrust-bearing apparatus 700 ₁ (FIG. 7) isoperably coupled to the downhole drilling motor 904. A secondthrust-bearing apparatus 700 ₂ (FIG. 7) is operably coupled to theoutput shaft 906. A rotary drill bit 908 configured to engage asubterranean formation and drill a borehole is connected to the outputshaft 906. The rotary drill bit 908 is shown as a roller cone bitincluding a plurality of roller cones 910. However, other embodimentsmay utilize different types of rotary drill bits, such as a so-called“fixed cutter” drill bit shown in FIGS. 6A and 6B. As the borehole isdrilled, pipe sections may be connected to the subterranean drillingsystem 900 to form a drill string capable of progressively drilling theborehole to a greater depth within the earth.

A first one of the thrust-bearing assemblies 702 of the thrust-bearingapparatus 700 ₁ is configured as a stator that does not rotate and asecond one of the thrust-bearing assemblies 702 of the thrust-bearingapparatus 700 ₁ is configured as a rotor that is attached to the outputshaft 906 and rotates with the output shaft 906. The on-bottom thrustgenerated when the drill bit 908 engages the bottom of the borehole maybe carried, at least in part, by the first thrust-bearing apparatus 700₁. A first one of the thrust-bearing assemblies 702 of thethrust-bearing apparatus 700 ₂ is configured as a stator that does notrotate and a second one of the thrust-bearing assemblies 702 of thethrust-bearing apparatus 700 ₂ is configured as a rotor that is attachedto the output shaft 906 and rotates with the output shaft 906. Fluidflow through the power section of the downhole drilling motor 904 maycause what is commonly referred to as “off-bottom thrust,” which may becarried, at least in part, by the second thrust-bearing apparatus 700 ₂.

In operation, drilling fluid may be circulated through the downholedrilling motor 904 to generate torque and effect rotation of the outputshaft 906 and the rotary drill bit 908 attached thereto so that aborehole may be drilled. A portion of the drilling fluid may also beused to lubricate opposing bearing surfaces of the bearing elements 706of the thrust-bearing assemblies 702.

FIG. 10 is a side cross-sectional view of an embodiment of awire-drawing die 1000 that employs a PDC 1002 fabricated in accordancewith the teachings described herein. The PDC 1002 includes an inner,annular PCD region 1004 comprising any of the PCD tables describedherein that is bonded to an outer cylindrical substrate 1006 that may bemade from the same materials as the substrate 302 shown in FIG. 3A. ThePCD region 1004 also includes a die cavity 1008 formed therethroughconfigured for receiving and shaping a wire being drawn. Thewire-drawing die 1000 may be encased in a housing (e.g., a stainlesssteel housing), which is not shown, to allow for handling.

In use, a wire 1010 of a diameter d₁ is drawn through die cavity 1008along a wire drawing axis 1012 to reduce the diameter of the wire 1010to a reduced diameter d₂.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall have the same meaning as the word“comprising” and variants thereof (e.g., “comprise” and “comprises”).

1. A method of fabricating a polycrystalline diamond compact,comprising: forming a polycrystalline diamond body in a firsthigh-pressure/high-temperature process performed at a first pressure;leaching the polycrystalline diamond body to at least partially remove acatalyst therefrom, thereby forming an at least partially leachedpolycrystalline diamond body; and subjecting the at least partiallyleached polycrystalline diamond body and a substrate to a secondhigh-pressure/high-temperature process, at a second pressure, toinfiltrate the at least partially leached polycrystalline diamond bodywith an infiltrant, wherein the second pressure of the secondhigh-pressure/high-temperature process is less than the first pressureof the first high-pressure/high-temperature process.
 2. The method ofclaim 1 wherein forming a polycrystalline diamond body in a firsthigh-pressure/high-temperature process performed at a first pressureincludes sintering a plurality of diamond particles in the presence ofthe catalyst at a pressure of at least about 7.5 GPa cell pressure. 3.The method of claim 1 wherein the first pressure of the firsthigh-pressure/high-temperature process is about 9 GPa to about 12 GPacell pressure, and the second pressure of the secondhigh-pressure/high-temperature process is at least about 7.5 GPa cellpressure.
 4. The method of claim 1 wherein the plurality of diamondparticles exhibits an average diamond particle size of about 30 μm orless.
 5. The method of claim 4 wherein the polycrystalline diamond bodyexhibits a coercivity of about 115 Oersteds (“Oe”) or more, and aspecific magnetic saturation of about 15 Gauss·cm³/grams (“G·cm³/g”) orless.
 6. The method of claim 5 wherein the coercivity is about 115 Oe toabout 250 Oe, and the specific magnetic saturation is about 5 G·cm³/g toabout 15 G·cm³/g.
 7. The method of claim 1, further comprising leachingthe infiltrated polycrystalline diamond body to at least partiallyremove the infiltrant therefrom.
 8. The method of claim 1 wherein theinfiltrant includes a metallic infiltrant.
 9. The method of claim 8wherein the metallic infiltrant includes cobalt.
 10. The method of claim1 wherein the substrate includes the infiltrant.
 11. The method of claim1 wherein the catalyst includes a metal-solvent catalyst.
 12. The methodof claim 1 wherein forming a polycrystalline diamond body in a firsthigh-pressure/high-temperature process performed at a first pressureincludes forming the polycrystalline diamond body on a cemented carbidesubstrate.
 13. The method of claim 1 wherein the polycrystalline diamondbody includes greater than 0 weight % to about 7.5 weight % of thecatalyst.
 14. A method of fabricating a polycrystalline diamond compact,comprising: sintering a plurality of diamond particles in the presenceof a metal-solvent catalyst to form a polycrystalline diamond body;leaching the polycrystalline diamond body to at least partially removethe metal-solvent catalyst therefrom, thereby forming an at leastpartially leached polycrystalline diamond body; and subjecting anassembly of the at least partially leached polycrystalline diamond bodyand a cemented carbide substrate to a high-pressure/high-temperatureprocess to infiltrate the at least partially leached polycrystallinediamond body with an infiltrant, wherein a pressure of thehigh-pressure/high-temperature process is less than that employed in theact of sintering of the plurality of diamond particles.
 15. The methodof claim 14 wherein the pressure at which the plurality of diamondparticles is sintered is about 9 GPa to about 12 GPa cell pressure, andthe pressure of the high-pressure/high-temperature process used toinfiltrate the leached polycrystalline diamond body is at least about7.5 GPa cell pressure.
 16. The method of claim 14 wherein the pluralityof diamond particles exhibits an average diamond particle size of about30 μm or less.
 17. The method of claim 16 wherein the polycrystallinediamond body exhibits a coercivity of about 115 Oersteds (“Oe”) or more,and a specific magnetic saturation of about 15 Gauss·cm³/grams(“G·cm³/g”) or less.
 18. The method of claim 17 wherein the coercivityis about 115 Oe to about 250 Oe, and the specific magnetic saturation isabout 5 G·cm³/g to about 15 G·cm³/g.
 19. The method of claim 14 whereinthe cemented carbide substrate includes chromium carbide.
 20. A methodof fabricating a polycrystalline diamond compact, comprising: sinteringa plurality of diamond particles in the presence of a metal-solventcatalyst to form a polycrystalline diamond body, wherein the pluralityof diamond particles exhibits an average particle size of about 20 μm orless, wherein the polycrystalline diamond body exhibits a coercivity ofabout 115 Oersteds or more, wherein the polycrystalline diamond bodyexhibits a specific magnetic saturation of about 15 Gauss·cm³/grams orless, and wherein the polycrystalline diamond body includes betweenabout 0 weight % to about 6 weight % of the metal-solvent catalyst; atleast partially removing the metal-solvent catalyst from thepolycrystalline diamond body to form an at least partially leachedpolycrystalline diamond body; and subjecting an assembly of the at leastpartially leached polycrystalline diamond body and a cemented carbidesubstrate to a high-pressure/high-temperature process to infiltrate theat least partially leached polycrystalline diamond body with aninfiltrant from the cemented carbide substrate, wherein thehigh-pressure/high-temperature process is performed at a pressure lessthan that employed in the act of sintering of the plurality of diamondparticles.